1. Field of the Invention
The present invention relates to a pneumatic tire.
2. Description of the Related Art
Generally, the tread of a pneumatic tire for vehicles is provided with a large number of grooves in order to secure various performances such as drain performance, braking performance and heat generation, and a number of blocks are formed in a compartmentalized manner by those grooves.
On the other hand, in general, when a tire runs, cracks are generated at the bottoms of the grooves or at the areas where the walls of blocks meet the bottoms of the grooves. Important causes of these groove cracking include the occasion when excessive lateral force is generated in the blocks of the tread depending on the use condition of the vehicle and the pavement state of the road, and cracks are generated in the grooves; the occasion in which as excessive level differences are formed in the road, fatigue and impact are transferred to the tire, and thus cracks are generated in the grooves; and the occasion in which foreign materials such as pebbles go into the grooves during the running of the vehicle and penetrate further into the inside, and thus cracks are generated in the grooves. Due to these causes, serious problems may occur in the product quality, performance and the like of the tire.
In order to solve the problems described above, technologies that enable prevention of the phenomenon of cracking through the design of the round values of the groove bottoms or the design of the groove width, have been suggested. However, these techniques have negligible effects of preventing the generation of cracks, and particularly, these technologies have a problem of being unable to fundamentally prevent the phenomenon in which cracks are generated in the grooves because grooves are continuously deformed as a result of the movement of the blocks that are contacted with the ground surface at the time of continuous running or steering of the vehicle (see Japanese Patent Application Laid-Open No. 2007-223480 (filed Sep. 6, 2007)).